Whenever someone complains about why their shared video link on YouTube ‘won’t work’.
It works, but people largely forgot that Google stupidly ruined that ability for everyone by making it mandatory that you be logged in to watch videos, so you’re not flagged as a bot. But, since you’re sharing a link to the video or embedding it, you can’t watch it anyways because the stupid prompt shows up, forcing you to go to the site itself.
The Search Function on almost any platform.
Hundreds of posts asking the same question on a particular topic on enthusiast or hobby pages….these bury actual new topics & discussions.
Or people on buy/sell/trade pages looking for certain items, when there’s multiple posted within the last few days, and are still available.
I think there’s a perfect middleground between banning reposting existing topics and no moderation. You don’t want to create a StackOverflow situation where people can’t ask a question because someone asked a similar one 15 years ago